Marine propeller



0. A. WIRKKALA MARINE PROPELLER Filed Feb. 4, 1958 April 4, 1961 INVENTOR. 0564/8 Fl. h/neKKnL/l d'J-ww MAR-INE'PROPELLER: Oscar-1A. Wir'kkala,-342. 18th.Ave., Seattle, wash.

Filed Feb'. 4; 1958,8er: No. 713,148

1 claim. cl. 170-170 This invention relates to screw" propellers of those kinds-designedforthe propulsion of marine-vessels.

It is the principalobject of this invention to provide propellers that may beemployed for-the driving of marine Vessels ofall typesand sizes, including its use for the propulsion ofspeed boats, pleasure boats, and hydroplanes 'employing eitherinboard or outboard motors.

More specificallyjstated, the present invention resides in" anovel propeller blade-designthat will reduce vibra tion; as caused by the propeller action; to-aminimum; that will effect a material reduction in the usual noise that is incident to. propeller operation; that wil1.bring about a substantial reduction in fuel consumption with an increase in speed of travel of the vessel towhich it is applied It; is? a:further. objectof the. invention to provid'ea propeller blade. design that. overcomes :cavitatio'n' andlprevents thegfrmatiomof. vacuum pockets? immediatelysback ofthe propeller hub;.. that has a a nm slip drivingaactioit and produces practically no wake of bubbles.

Yet another object of the invention is to provide a propeller that embodies certain features of blade design whereby suction pockets back of the propeller are eliminated; to provide a blade design characterized by the provision of a certain relief passage in its trailing edge and adjacent the hub and by the flanging of the blade at the inner and outer limits of its trailing edge in such United States atom manner as to effect .a separation of the water that slips from the trailing edge and that which must pass through the relief passage to overcome cavitation.

Still further objects and advantages of the invention are to be found in the details of construction and relation ship of parts embodied by the propeller, as will hereinafter be fully described. v

In accomplishing the above mentioned and other objects of the invention, I have provided the improved details of construction, the preferred forms of which are illustrated in the accompanying drawings, wherein:

- Fig. 1 is a face view of the .rear or pressure side of a propeller embodying the improvements of the present invention therein.

Fig. 2 is a section of the propeller, taken on line 2-4 in Fig. 1; particularly showing the location of the suction relief passage.

Fig. 3 is a series of sectional views of a blade, taken on lines aa; b-b and cc, respectively, in Fig. 1.

Fig. 4 is a perspective view of the propeller of Fig. 1, showing the forward faces of the blades.

Referring more in detail to the drawings.

In Fig. l, I have shown a three bladed propeller, each blade 10 of which is identical in all respects to the others, and all blades of which are in this instance, formed integrally with a hub 12 that is formed axially with a tapered bore 13 for mounting the propeller in the usual way on a propeller shaft. The diameter of the propeller; its number of blades and their pitch can be increased or decreased to suit the particular water craft on which the propeller is to be used. However, in pro- Fat-tented Apr. 4,1961

pellers for all uses and of all sizes, regardless of pitch and diameter, the. characterizing features of the'blades are the same- As herein shown, the three-propeller blades. 10 are equally angularly spaced about the hub 12' and each extends through an arcuate' segmentv of approximately from its forward edge to trailing edge, thus leaving substantial clearance between blades asrwill beunden stoodby referenceto'Figs. l and 4. Each blade 10 is joined to the hub portion through thermediacy of a neck portion n which, at its juncture with the cylindrical hub; has an arcuate width or span of approximately 80 de grees; and its extent along'the-hub is'approximately to the. full length of the hub, as: observed in Fig. 2.

Each blad'eltl'has a forward or leading edge-ISrthat starts from a point of the neck portion near the hub, closely adjacentits forward end, and curves outwardly from thehub andrearwardly in aspiral direction. The curve of the outer peripheral edge portion, as from point 11 to pointc in Fig. l, is centered in the axial line of the hub. The" rearward ortrailing edge of the blade is designated at 18 and it is shown in" Figs. 1. and 2 to be'substantially straight and also substantially perpendicular to the hub axis; The pitch of. the blades maybe varied to suit requirements or:desires. However, throughout: its full extent the pitch :of; each blade isuniform and iszsuch that, in operation, there will be substantially no. water slippage radially thereof, and'all propelling forces exerted by the blades are caused to be directed parallel to the-axial line: of the, hub; thedirectionof these forcesbeing as indicated-by. the-arrowsfin Fig.1 4;-

One of the characterizing features of the present pro; peller blade design resides inthe; terminationof. the straight trailing edge 18 of each blade at a short distance from the hub, as at 19 in Fig. 1, then forming the neck portion it within htat point with a substantially semicylindrical recess 20. This recess is in the nature of a relief passage 21 leading in a direction lengthwise of the hub and through which water under compression at the forward side of the blade can escape rearwardly to fill the cavity that forms at the back side of the blade incident to the rotation of the propeller. For example, in reference to the propeller as seen in Fig. 2 and considering it to be rotating in a direction for driving the vessel in the direction of arrow x, there will be a tendency to produce cavitation or a vacuum pocket back of the hub, for example, within the dash enclosed area y. Also, there is a tendency to build up a high pressure of water against the forward sides of the blades. By the provision of the relief passages 21, the retarding effect of this built up pressure as well as the retarding effect of cavitation is eliminated by the ready escape of the water under pressure through the relief passages 21 to the vacuum pockets. This relief of pressure and elimination of suction or cavitation has various beneficial results including elimination of propeller vibration; the reduction in propeller noise and the elimination of the usual bubble wake created by propeller action. Incidental advantages are noted in an increase of speed; in the lessening of fuel consumption and in the quicker acceleratioin.

To further increase the efficiency of the propeller as above described, I have formed that arcuate edge portion of each blade that is centered in the axial line of the hub, as for example from point b to point c in Fig. 1, on the pressure side of the blade, with a water retaining flange 25. Also, at the inner end of the trailing edge of each blade, I have provided a rearwardly directed flange 26. This also extends along the outer edge of the recess 20 in an are centered on the axial line of the hub. When the propeller is rotating for a forward driving action, the slippage of water from the trailing edge of the blade is indicated by the arrows s applied across this edge in Fig.

1. This results not only in a direct rearward application of driving forces but also causes a separation of the water stream as it slips from the trailing edge, from that which is under pressure and which is escaping from the forward side of the blades through thepassages 21 to the back side thereof where it relieves cavitation, vacuum and suction. The single feature of the flange 26 is of great importance, and it has resulted in a substantial increase in efiiciency of the propeller. Propellers of this kind are especially desirable for all types of marine vessels, particularly those which may be used in naval operations. When such propellers are applied to submarines, the primary advantages are: the

noiseless operation; the absence of vibration and lessening l of noise. When used with any kind of marine vessel, a

saving of fuel is noted; greater speed is obtained, vibration is overcome and noise and wake are eliminated.

Such propellers may be cast of metal, or made of fiber glass or other materials of suitable kind and in sizes suitable for the various types of boats or vessels mentioned.

It is to be explained further that blade configuration as shown in Fig. 1 may be changed to some extent for what may be referred to as slow turning propellers. For example, for those which rotate at less than 500 revolutions per minute. Slow turning propellers are generally used on under water craft, such as submarines, and on tunnel boats. To better adapt the propellers to such boats, the blades are extended, as has been indicated by dash lines in Fig. 1 wherein the extensions indicated at x, y and 2, represent the change for propellers which would rotate at 300, 400 and 500 revolutions per minute, respectively. Slow turning propellers also are more eflicient when the recesses are increased in size.

In view of the above, it is not the intent that the propeller design be confined to any specific or fixed blade configuration.

What I claim as new is:

A marine'propeller of the character described having a hub portion and a plurality of equidistamly spaced blades extending radially outwardly therefrom, each blade having a substantially straight trailing edge portion that extends substantially radially of the hub axis and each blade having a neck portion in that region immediately adjacent the hub, each blade also having a circumferentially extending outer edge disposed on a radius of curvature having its center substantially coincidental with the axis of said hub with such circumferential edge portion extending from said trailing edge to merge smoothly with the leading edge of the blade which extends therefrom back to said hub, the trailing side of each neck having an arcuate recess with the outer edge thereof being disposed on a radius of curvature spiralling from said trailing edge inwardly toward the axis of said hub with each neck providing a suction relief passage immediately adjacent to the hub, said outer edge of the neck portion having a flange thereon extending from said leading edge and spiralling inwardly thereof toward the axis of said hub and said circumferential edge portion of the blade having a laterally directed flange thereon extending from said trailing edge towards said leading edge, said flange on the circumferential edge of the blade being of material greater length than the flange on the outer edge of said neck portion whereby the two flanges, with the blade portion therebetween, define a channel extending from the region of the leading edge of the blade to the trailing edge of the blade.

' References Cited in the file of this patent UNITED STATES PATENTS 996,741 Wait July 4, 1911 1,030,047 Ames June 18, 1912 1,031,415 Boutwell July 2, 1912 2,023,111 Alsing Dec. 3, 1935 2,599,598 Wirkkala June 10, 1952 

